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Proceedings Paper

Frequency-domain measurements of changes of optical pathlength during spreading depression in a rodent brain model
Author(s): Michael B. Maris; Avraham Mayevsky; Eva Marie Sevick; Britton Chance
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Paper Abstract

Previously, we have shown that time-resolved spectroscopy can monitor changes in the distribution of photon migration pathlengths which are reflective of the changes in the tissue absorption due primarily to oxygenated or deoxygenated hemoglobin. In this study, we have monitored mean photon migration pathlengths in the frequency domain in the rodent brain insulted by hypoxia, ischemia and spreading depression (SD) using phase modulated spectroscopy (PMS). This technique consisted of monitoring light which emerged from the exposed rodent skull at 8 mm form an incident light source of 754 nm and 816 nm whose intensity was modulated at 220 MHz. The changes in phase-shift, (theta), of the emergent light with respect to the incident light are reflective of the photon pathlengths and hemoglobin absorbance. A multiprobe assembly holding PMS source fiber, nicotinamide dinucleotide (NADH) fluorometric probe, electrocortigraph (ECoG) electrodes, and doppler blood flow probe was placed on the rodent brain to simultaneously monitor brain metabolism, electrical cortical activity (ECoG) and blood flow. The PMS detector fiber was placed 8 mm posterior to the multiprobe assembly. Correlations between changes in intracellular deoxygenation (NADH) and hemoglobin deoxygenation as measured by PMS changes at 754 nm and 816 nm during hypoxia, and ischemia were found. The depolarization phase of spreading depression resulted in a similar increase at both 754 nm and 816 nm. We attribute this result to vasoconstriction and/or the decrease of extracellular space due to water shift in the rodent brain.

Paper Details

Date Published: 1 May 1991
PDF: 13 pages
Proc. SPIE 1431, Time-Resolved Spectroscopy and Imaging of Tissues, (1 May 1991); doi: 10.1117/12.44185
Show Author Affiliations
Michael B. Maris, Univ. of Pennsylvania School of Medicine (United States)
Avraham Mayevsky, Univ. of Pennsylvania School of Medicine (USA) and Bar-Ilan (Israel)
Eva Marie Sevick, Univ. of Pennsylvania School of Medicine (United States)
Britton Chance, Univ. of Pennsylvania (United States)

Published in SPIE Proceedings Vol. 1431:
Time-Resolved Spectroscopy and Imaging of Tissues
Britton Chance, Editor(s)

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